diff --git a/library/includes/ucp/register.php b/library/includes/ucp/register.php
index 53d5bae2b..62f1f7ed0 100644
--- a/library/includes/ucp/register.php
+++ b/library/includes/ucp/register.php
@@ -142,6 +142,7 @@ switch ($mode) {
         if (!$pr_data = DB()->fetch_row($sql)) {
             bb_die($lang['PROFILE_NOT_FOUND']);
         }
+        $pr_data['user_birthday'] = $pr_data['user_birthday']->format('Y-m-d');
         if (IN_DEMO_MODE && isset($_COOKIE['user_lang'])) {
             $pr_data['user_lang'] = $_COOKIE['user_lang'];
         }
diff --git a/library/includes/ucp/viewprofile.php b/library/includes/ucp/viewprofile.php
index 3d4605e68..e9f8903a7 100644
--- a/library/includes/ucp/viewprofile.php
+++ b/library/includes/ucp/viewprofile.php
@@ -30,6 +30,8 @@ if (!$profiledata = get_userdata($_GET[POST_USERS_URL], profile_view: true)) {
     bb_die($lang['NO_USER_ID_SPECIFIED']);
 }
 
+$profiledata['user_birthday'] = $profiledata['user_birthday']->format('Y-m-d');
+
 if (!$ranks = $datastore->get('ranks')) {
     $datastore->update('ranks');
     $ranks = $datastore->get('ranks');
diff --git a/src/Legacy/Common/User.php b/src/Legacy/Common/User.php
index 52bfafc01..77e844004 100644
--- a/src/Legacy/Common/User.php
+++ b/src/Legacy/Common/User.php
@@ -232,6 +232,7 @@ class User
             }
         }
 
+        $this->data['user_birthday'] = $this->data['user_birthday']->format('Y-m-d');
         return $this->data;
     }
 
diff --git a/viewtopic.php b/viewtopic.php
index 806327ded..6e7a2b9d2 100644
--- a/viewtopic.php
+++ b/viewtopic.php
@@ -565,6 +565,7 @@ for ($i = 0; $i < $total_posts; $i++) {
     $poster_from = ($postrow[$i]['user_from'] && !$poster_guest) ? $postrow[$i]['user_from'] : '';
     $poster_joined = !$poster_guest ? $lang['JOINED'] . ': ' . bb_date($postrow[$i]['user_regdate'], 'Y-m-d H:i') : '';
     $poster_longevity = !$poster_guest ? delta_time($postrow[$i]['user_regdate']) : '';
+    $poster_birthday = $postrow[$i]['user_birthday']->format('Y-m-d');
     $post_id = $postrow[$i]['post_id'];
     $mc_type = (int)$postrow[$i]['mc_type'];
     $mc_comment = $postrow[$i]['mc_comment'];
@@ -715,7 +716,7 @@ for ($i = 0; $i < $total_posts; $i++) {
         'DELETE' => $delpost_btn,
         'IP' => $ip_btn,
 
-        'POSTER_BIRTHDAY' => user_birthday_icon($postrow[$i]['user_birthday'], $postrow[$i]['user_id']),
+        'POSTER_BIRTHDAY' => user_birthday_icon($poster_birthday, $postrow[$i]['user_id']),
 
         'MC_COMMENT' => $mc_type ? bbcode2html($mc_comment) : '',
         'MC_BBCODE' => $mc_type ? $mc_comment : '',